Field of the Invention
The invention relates to solid state relays and more particularly to use of isolation channels for implementing for solid state relays.
Description of the Related Art
Solid state relays (SSRs) have been used in place of mechanical relays in many applications. Traditionally, solid state relays have used optical isolation to transmit across the isolation barrier. FIG. 1 illustrates a traditional optical based solid state relay 101. There is no power supply available either on the transmit side or the receive side in the solid state relay 101. Instead, the solid state relay 101 receives a current 102 that turns on the light emitting diode 103. The emitted light turns on photodiodes 105, which turn on a field effect transistor (FET) 107. Thus, the current 102 controls the operation of the FET 107. When the current 102 is on, the FET 107 is on and when the current is off, the FET is off. Typically the FET 107 is located on the die with the photodiodes due to the low power available to drive the FET. Opto-based solid state relays, such as the one illustrated in FIG. 1, transmit low power due to the inefficiencies of the optical components and have high range of temperature variability. Such opto-based SSRs also tend to have slow turn on time (e.g., >1 ms) depending on the size of FET 107 as a larger FET would turn on more slowly given the same transmit power across the isolation channel.